Potential Surface Ice Distribution on Close-in Terrestrial Exoplanets around M dwarfs

TL;DR

This study models how orbital and atmospheric parameters influence surface ice distribution on close-in terrestrial exoplanets around M-dwarfs, highlighting the roles of spin-orbit ratio and obliquity in cold-trap regions.

Contribution

Developed a simple coupled land-atmosphere model to analyze surface ice distribution considering various orbital and atmospheric parameters on exoplanets with thin atmospheres.

Findings

Spin-orbit ratio and obliquity are key in cold-trap regions.

Incident stellar flux and surface pressure have limited effects under certain conditions.

Surface ice distribution can inform climate understanding of arid exoplanets.

Abstract

Previous studies suggested that surface ice could be distributed on close-in terrestrial exoplanets around M-dwarfs if heat redistribution on the planets is very inefficient. In general, orbital and atmospheric parameters play an important role in the climate on terrestrial planets, including the cold-trap region where the permanent surface water reservoir can potentially be distributed. Here, we develop a simple coupled land-atmosphere model to explore the potential surface ice distribution on close-in terrestrial planets with various orbital and atmospheric parameters, assuming that the planets are airless or have a thin \ce{N2} atmosphere. We find that the most significant factors in deciding the surface cold trap region are the spin-orbit ratio and obliquity. The incident stellar flux and the surface pressure play a limited role in the thin \ce{N2} simulations for incident flux smaller than Mercury's and surface pressure lower than 10$^4$ Pa. Our result illustrates the possible distribution of surface ice on arid terrestrial planets and can help to understand the climate of these exoplanets.